Application of a CHA-type zeolite membrane to the esterification of adipic acid with isopropyl alcohol using sulfuric acid catalyst

CHA-type zeolite membranes show extremely high dehydration performance and high acid stability. This study applied the membrane to the esterification of adipic acid with isopropyl alcohol using sulfuric acid as the catalyst. The membrane was placed in the vapor phase to avoid direct contact with sulfuric acid, and water vapor was removed by vapor permeation. A numerical kinetic model was constructed to understand the effect of dehydration by the membrane, and the experimental results were compared with the model predictions. The yield of diisopropyl adipate increased from 56% to 98% by membrane assistance. Moreover, the ester was produced in the high efficiency (yield>90%) despite the small membrane (35–80 cm2 per kg of reactant), since the permeation flux of the membrane was significantly high. These results suggest that assistance by a CHA-type zeolite membrane is effective for the ester condensation reaction of adipic acid with isopropyl alcohol. This paper also discussed the stability of the membrane under the reaction conditions.